QuickLinks -- Click here to rapidly navigate through this document
Exhibit 5 and 23.1
September 29, 2003
Abbott Laboratories
100 Abbott Park Road
Abbott Park, Illinois 60064-6400
Ladies and Gentlemen:
I am Senior Vice President, Secretary and General Counsel of Abbott Laboratories, an Illinois corporation, and have advised Abbott Laboratories in connection with the proposed offering of 2,000,000 shares of the common stock, without par value, of Abbott Laboratories (the "Shares") pursuant to the Abbott Laboratories Affiliate Employee Stock Purchase Plan (the "Plan"), being offered pursuant to the Registration Statement on Form S-8 to which this is an exhibit (the "Registration Statement"). The Registration Statement is being filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended. In connection with the proposed offering and registration, I, or members of my staff, have examined or are otherwise familiar with:
- (i)
- the Registration Statement,
- (ii)
- the Restated Articles of Incorporation of Abbott Laboratories,
- (iii)
- the By-laws of Abbott Laboratories,
- (iv)
- the Plan, and
- (v)
- the minutes of all of the meetings of the board of directors of Abbott Laboratories relating to the establishment of the Plan.
In addition, I have made such other examinations and have ascertained or verified to my satisfaction such additional facts as I deem pertinent under the circumstances.
On the basis of such examinations, I am of the opinion that all of the legal and corporate proceedings that are necessary in connection with the grant of benefits under the Plan and the authorization and issuance of the Shares pursuant thereto have been duly taken and, after those Shares have been issued in accordance with the provisions of the Plan, those Shares will be legally issued, fully paid and nonassessable outstanding common shares of Abbott Laboratories.
I hereby consent to the filing of this legal opinion as an exhibit to the Registration Statement on Form S-8 to be filed by Abbott Laboratories with the Securities and Exchange Commission under the Securities Act of 1933, as amended, with respect to the Shares issuable pursuant to the Plan and to the reference to me under the caption "Interest of Named Experts and Counsel" in such Registration Statement.
Very truly yours,
Jose M. de Lasa
Senior Vice President,
Secretary and General Counsel
QuickLinks
